The invention pertains to a guide wire, especially for the percutaneous introduction of a balloon dilatation catheter into a blood vessel, with an elongated flexible shaft that contains a proximal end and a tapered distal end, and having a flexible spiral (helical coil) that surrounds the distal end of the shaft and is attached to it. The helical coil contains a distal radiographically visible part, a proximal radiographically invisible part and connection agents for the joining of the two parts of the helical coil.
Guide wires are known in several versions. For the introduction of a balloon catheter into a blood vessel, the guide wire is inserted into the blood vessel with the aid of a guide catheter, and the balloon catheter is pushed onto the guide wire and advanced in the vessel until the spot intended for treatment is reached. In the placement of the guide wire it is important that its distal end is steerable within the blood vessel and is visible on the X-ray screen. Furthermore, it should also be possible to make the region of the blood vessel intended for treatment visible with the aid of a contrasting agent. To assure that the distal end of the guide wire has the smallest negative effect on the visibility of the vessel, with the guide wires of the known design only a frontal section of the helical coil is opaque to X-rays and, therefore, easily visible. The two parts of the helical coil have to be securely connected to each other, so that breakage of the helical coil during treatment can be eliminated. On the other hand, the connection of these two parts should not diminish the steerability and the flexibility of the guide wire.
In the guide wire according to U.S. Pat. No. 4,922,924, both parts of the helical coil are turned (screwed) into each other over several stretched turns (coils). At the ends of the bifilar section, both parts are soldered to each other and to the central shaft. A safety wire is inserted in the helical coil with one end connected to the shaft and the other end connected to the distal tip of the guide wire. This safety wire is intended to assure that the helical coil can be bent into a certain form and that in case of breakage of the helical coil the distal part of the helical coil cannot separate from the shaft.
U.S. Pat. No. 4,748,986 shows a similar guide wire, in which also a distal part of the helical coil is screwed into a proximal part and is soldered together with it and also with the shaft. The soldered area extends here over the entire bifilar section, and this guide wire is also provided with a safety wire that connects the tip with the shaft.
The critical points in these guide wires are each located at the proximal and distal ends of the bifilar section. There, the turns of the helical coil are separated by (a distance equal to) the wire diameter of the helical coil, so that the respective other helical coil can be screwed into it. This space between the coils is filled in the bifilar section by the opposing second helical coil. At a certain distance from the bifilar section, the space between the coils is again normalized to a smaller dimension. However, an area that is sensitive to buckling is created between the bifilar section and the helical coil where the space between the coils is normal, since the second helical coil is missing there, but the space between the coils is not yet normalized.
Another problem is created in the assembly of the helical coils. They have to be precisely positioned for screwing them together, and be held such that both helical coils are situated in the assembled state in perfect alignment and do combine after soldering to a smooth, stepless continuous guide wire.
WO 92/04072 describes a guide wire that at its distal end is provided with two helical coils in coaxial alignment to each other. Of these, a smaller inner helical coil is on one end soldered to the shaft. The other, larger helical coil is at the distal end soldered to a tip of the guide wire, and is at proximal portions soldered to the shaft and a proximal part of the inner helical coil. Guide wires with two coaxial helical coils are also known from U.S. Pat. No. 5,144,959 and U.S. Pat. No. 5,063,935. The inner helical coil is at the proximal end connected with the shaft, and at the distal end with the tip of the guide wire.